Re: sudden severe stomach pain and diarrhea
I would suggest mentioning it to your doctor. However, I have similar boughts of unpleasantness. Also try writing down exactly what you ingested and did for that day, and if/when it happens again compare the two.
Odd as it is, my trigger is cheap coffee. If I drink a cup somewhere that uses high quality, whole bean varieties, I'm fine. But if I order a cup at the diner down the street that uses Folgers, I'm in the bathroom with wretched cramps 20 minutes later.